Wheelchairs provide a means of transportation and mobility to hundreds of thousands of people worldwide. The designs of these basic devices have evolved over the years to be more comfortable, reliable, and user friendly. However, the propulsion and braking systems for manual wheelchairs remains problematic for many wheelchair users.
Generally, propelling a typical wheelchair requires the wheelchair user to create friction on the hand ring of the wheel by pressing against it while also applying a tangential force to rotate the wheel. Many factors affect the efficiency of this propulsion system. For example, the force required to push a wheelchair varies due to changes in the terrain or incline. When ascending inclined terrain many wheelchair users experience difficulty providing the strength and endurance necessary to climb long or steep inclines. Similarly, when descending an inclined surface, users often find it difficult to control the speed of the wheelchair with the braking systems of typical wheelchairs. Thus, current wheelchair designs are not ideal for diverse surfaces and inclines.
Similarly, users of typical wheelchairs can brake or slow the wheelchair by applying friction between their hands and the hand rings on the wheels. This method of braking can wear the skin of the arms and hands of the user, thereby causing discomfort to the user. Additionally, slowing a chair in this manner can also damage the joints in the hands and wrists over time. Thus, friction provided by users' hands against the wheel while often the most common means of braking, can sometimes be dangerous and is not ideal.
Typical wheelchairs have existing wheel lock devices. However, these devices do not work well as a brake to slow the wheelchair while in motion. These locks are only meant to keep the wheelchair stationary, and often do not perform this function in many circumstances. An improved wheelchair brake is in high demand and continues to be sought.
Another problem of common manually powered wheelchairs is that the posture of a wheelchair user while pushing on hand rings can cause deviations in the angles of the user's wrists. These deviations can create high forces and stresses in the user's tendons that can result in injuries. Additionally, these stresses and forces on the user's wrists affect the ability of the user to grip and move the hand ring. Thus, some users have the strength to travel across most terrains and inclines while others may find it difficult to go up ramps that are specifically provided for wheelchairs.
Attempts to solve these problems have been unable to develop a design that successfully applies to a mainstream wheelchair. A few existing designs use levers to propel the wheelchair in place of the hand ring. Gearing devices have also been implemented on some of these alternative wheelchair designs to alter the user's mechanical advantage. Unfortunately, these designs often sacrifice other advantages of current wheelchairs such as comfort, maneuverability, easily removable wheels, or minimal chair width and weight.
Many wheelchair users desire a device that will make propelling their wheelchair easier and less damaging to their body. An improved wheelchair brake is also in high demand and continues to be sought.